JPH0238937A - Leak detecting device for pressure container - Google Patents

Abstract

PURPOSE:To decide whether or not there is a leak by comparing signals of >=3 acoustic sensors fitted on the external wall of a pressure container with normal signals and to identify the position of the leak from an arrival time difference between every two combined acoustic signals. CONSTITUTION:The outputs of the acoustic sensors 2a-2d fitted on the external wall 1 of a condenser body are sent to preamplifiers 3a-3d and main amplifiers 4a-4d, whose outputs are sent to a leak decision device 8 and compared with a previously set threshold value to decide whether or not there is a leak. The signals from the main amplifiers 4a and 4b, and 4c and 4d are inputted to mutual correlation analyzing devices 5a and 5b, whose outputs, i.e. acoustic signal arrival time difference signals 6a and 6b are used by a leak position identifying device 7 to identify the position of the leak. Consequently, the leak occurrence is detected and its position is securely identified without stopping the plant.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Field of Application) When a leak occurs in a pressure vessel, the present invention immediately detects the leak and identifies the leak position.

(Prior Art) Various pressure vessels are used in power plants, chemical plants, and the like.

These pressure vessels are generally manufactured under sufficient quality control and put into service after undergoing strict final inspections, but sometimes leaks may occur.

Causes of leaks in pressure vessels include minute racks, cracks in welds, loosening of flanges, and deterioration of gaskets. The causes of these leaks are often accompanied by changes over time, and are often not detected during pressure-tightness tests or water filling tests when the pressure vessel is completed.

If a leak occurs in a pressure vessel, there is a risk of explosion or fire if the internal fluid is, for example, a flammable substance, and if the pressure vessel is used in an energy conversion plant such as a Rankine cycle, it can significantly reduce the efficiency of the plant. This will result in a decline in Furthermore, if the internal fluid is steam or air, it is difficult to detect leaks by visual inspection, especially if the inside of the pressure vessel is under negative pressure, such as in a condenser at a steam power plant, and leaks from the outside are difficult to detect. In this case, it becomes even more difficult to detect leaks from outside.

The most reliable way to detect and locate a leak is to shut down the plant and perform a hermetic leak test. However, stopping a plant not only wastes energy, but also has a major impact on related facilities and peripheral equipment.

(Question 8 to be solved by the invention) As explained above, the hermetic leak test method requires the plant to be stopped, which not only wastes energy but also causes a large E'S to related facilities and peripheral equipment. In addition, the method of relying on the five senses of the workers required work in a dangerous environment, which caused significant delays in terms of safety management.

The present invention has been made to solve the above problems, and is a pressure vessel leak detection system that can reliably detect the occurrence of a leak and identify its position without stopping the plant when a leak occurs in a pressure vessel. The purpose is to provide a device.

[Structure of the Invention] (Means for Solving the Problems) The pressure vessel leak detection device of the present invention includes three parts on the outer wall of the pressure vessel.
The sound propagating through the outer wall is measured by installing more than one acoustic sensor in a non-linear manner, and the signals from these acoustic sensors are guided to a leak determination device via a preamplifier and a main amplifier, and compared with the acoustic signal under normal conditions. By doing so, it is determined whether or not a leak has occurred, and the outputs of the acoustic sensors are combined two by two and input into a cross-correlation analyzer to calculate the acoustic signal arrival time difference, and a signal indicating the acoustic signal arrival time difference is generated. The present invention is characterized in that the leak position is identified by inputting the information to a leak position identification device.

(Function) In the pressure vessel leak detection device of the present invention configured as described above, when there is no leak, the signal from the acoustic sensor is background noise (BGN) and has a very small output. The signals amplified by the preamplifier and main amplifier are also small, and the leakage determination device also determines that there is no leakage.

On the other hand, when a leak occurs, the fluid flows through a very small gap, which causes turbulence, shock waves, and vibrations due to condensation, evaporation, and the like. Since a part of this vibration energy propagates through the outer wall, the output of the acoustic sensor becomes large, and the signal amplified through the preamplifier and main amplifier also becomes large. Therefore, the leak determination device determines that a leak has occurred.

Furthermore, the cross-correlation analysis device calculates the acoustic signal arrival time difference of the signals from the plurality of acoustic sensors, and the leak position identification device identifies the leak position.

(Example) Next, the present invention will be explained in detail with reference to FIG.

In this embodiment, a condenser in a steam power plant where the internal pressure is negative and it is considered particularly difficult to identify the leak position will be explained.

Four acoustic sensors 2as2b, 2 are installed on the outer wall 1 of the condenser body.
c, 2d are attached. These acoustic sensors 2a
The output from ~2d is preamplified by preamplifiers 3a, 3b, 3c, and 3, which have the function of amplifying and removing signals in unnecessary frequency bands.
d and main amplifiers 4a, 4b, 4cs and 4d.

The signals from the main amplifiers 4as4c are input to the cross-correlation analyzer 5a. In addition, the main amplifier 4b,
The signal from 4d is input to the cross-correlation analyzer 5b.

Acoustic signal arrival time difference signals 6a and 6b outputted from these cross-correlation analysis devices 5g and 5b are manually input to a leak position identification device 7. Further, the signals from the main amplifiers 4a to 4d are also sent to the leakage determination device 8.

In this specification, for convenience of explanation, the devices within the broken line in FIG. 1, that is, the cross-correlation analysis devices 5a and 5b, the leak position identification device 7, and the leak determination device 8, will be collectively referred to as a calculation section.

In the device of the present invention having such a configuration, when there is no leakage in the outer wall 1 of the condenser body, the acoustic sensors 2a to 2d detect sound waves propagating from the upper turbine body and the piping connected to the condenser. Only background noise (BGN) is measured, which mainly includes the sound coming from the air, the sound from cooling water flowing in the icebox or cooling pipes, the sound from the exhaust from the turbine, and the sound associated with condensation.

Therefore, preamplifiers 3a to 3d, main amplifiers 48 to 4d
Furthermore, the signal output from which unnecessary frequency band signals are removed so as to efficiently remove the BGN mentioned above is also small, so that the leak detection device 8 detects the leak detection signal when the human power is below a preset threshold. No output.

On the other hand, for example, as shown in FIG.
When a leak occurs at a point X at distances g1, g2, g3, and g4 from d, the acoustic output from each acoustic sensor 2a to 2d becomes larger than when there is no leak, as shown in FIG. , preamplifier 38~3d, main amplifier 48
The signal amplified and filtered by ~4d also becomes large.

The leak determination device 8 outputs a leak detection signal and an estimated leak amount when the magnitude of the acoustic signal exceeds a preset threshold.

The sound caused by leaks fluctuates in complex cycles and amplitudes, as shown in Figure 3, due to the influence of internal and external pressure, flow velocity, and the condenser shell, which vibrates minutely at various cycles. These sounds give a phase difference to each acoustic sensor due to the difference in distance from the leak occurrence position. For example, when the acoustic sensors 2a to 2d and the leak position X are located at the positions shown in FIG.
The output of s2c is (gll
2) There will be a phase difference of /a. Therefore, when the mutual function of the outputs from the acoustic sensors 2a and 2c is determined by the cross-correlation analyzer 5a, it will show a peak when the time shift τ is τ+-(N+-u2)/a as shown in FIG. . Similarly, the mutual gap V between the outputs from the acoustic sensors 2b and 2d also shows a peak when τ2-(Ω3-11<)/a.

Conversely, when the cross-correlation analysis device 5a calculates the acoustic signal arrival time difference based on the output of the acoustic sensor 2a%2C, the locus of a point whose distance from the two points is constant is mathematically a hyperbola. Hyperbola 11 in Figure 5 can be drawn. Similarly,
Since a hyperbola 12 can be drawn from the acoustic signal arrival time difference τ2 of the acoustic sensors 2b and 2d, the leak occurrence position X can be identified from the intersection of these hyperbolas 11 and 12.

Therefore, when the leak determination device 8 detects a leak, the cross-correlation analysis devices 5a and 5b determine the acoustic signal arrival time difference τ
1, acoustic signal arrival time difference signal 6 a s 6 representing τ2
The leak ml can be identified by calculating b, guiding these signals to the leak position identification device 7, and performing calculations to find the intersection of hyperbolas 11 and 12.

In addition, in the above embodiment, four acoustic sensors 2a to
Although the example using the acoustic sensors 2d has been described, the present invention is not limited to this, and the number of acoustic sensors 2a to 2d may be three by sharing two of the four acoustic sensors 2a to 2d.

Furthermore, in FIG. 1, by inputting the leak position signal determined by the leak position identification device 7 to the leak determination device 8, the leak determination accuracy can be improved. Furthermore, the leak determination device 8 may perform determination using data obtained by converting acoustic output into a frequency domain.

FIG. 6 shows another embodiment of the invention. This embodiment shows an example in which the present invention is applied to a particularly large condenser shell, and a large number of acoustic sensors 2a, 2b, 2 are mounted on the outer wall 1 of the condenser shell.
C... is installed.

The outputs of these acoustic sensors 2a, 2b... are sent to preamplifiers 3a, 3b... and main amplifiers 4a14b...
After being amplified and having unnecessary frequency components cut, the signal is guided to a comparator 13 and a switch 14.

The comparator 13 roughly determines the leak position based on the magnitude of the outputs of the acoustic sensors 2a, 2b, . The switch 14 transfers only the signals from the four acoustic sensors 2a to 2d selected by the comparator 13 to the calculation unit 9.
(The configuration is the same as in FIG. 1) cross-correlation analysis device 5a,
5b and the leak determination device 8.

In the calculation unit 9, the four selected acoustic sensors 2a to 2d
As in the case of Fig. 1, the cross-correlation analyzer 52%
, τ2 are calculated, and these signals are guided to a leak position identifying device 7 to identify the leak position.

Therefore, according to this embodiment, even in a large pressure vessel, it is possible to accurately detect the occurrence of a leak and identify its position.

FIG. 7 shows another embodiment of the present invention, in which a vibration device 15 is installed on the outer wall 1 of the condenser body, and this vibration device is activated by a control signal from a control device 16. . Signals from the control device 16 are passed through filters 17a, 17b...
The direct influence of the vibration device is removed from the acoustic signals output from the main amplifiers 4a, 4b, . . . to the arithmetic unit 9.

That is, when a control signal is output from the control device 16, the vibration device 15 vibrates and transmits the vibration to the condenser body outer wall 1. The time when the vibration from the vibration device 15 arrives at the acoustic sensors 2a to 2d can be determined from the relationship between the vibration propagation speed and the distance. Further, due to the vibration of the condenser body outer wall 1, a small change in area occurs in a small leakage crack or the like. Therefore, the signals based on the acoustic outputs from the acoustic sensors 2a and 2c, from which the direct influence of vibration has been removed by the filters 17a to 17d, are as shown in FIG. Therefore, the cross-correlation function exhibits a sharp peak as shown by the solid line in FIG. 9, and the accuracy of the acoustic signal arrival time difference is improved, and as a result, the accuracy of identifying the leak position is also improved.

Incidentally, substantially the same effect can be obtained by using a horn 18 shown by a broken line in FIG. 7 instead of the vibration device 15 to apply sound waves to the external or internal fluid.

Generally, a large number of pipes are connected to a condenser, and a large number of valves and flanges are used therein, and the present invention can be applied to detecting and identifying leaks from these valves and flanges. You can also do it.

FIG. 10 shows an example in which the present invention is applied to a pressure vessel equipped with a stop valve 21 and a blind flange 22 on a piping 20 connected to the condenser body outer wall 1, and as in FIG. In addition to four acoustic sensors 2a to 2d provided on the outer wall 1 of the condenser body, the piping 20 also has 2fl! I acoustic sensor 23a
, 23b are attached.

In this way, the two acoustic sensors 23a and 23b attached to the piping 20, or one acoustic sensor attached to the piping 20 and the acoustic sensor 2a~ attached to the outer wall of the condenser body.
2d, it is possible to identify from which position in the piping 20 the leak is coming from in the same manner as described above.

[Effects of the Invention] As described above, according to the present invention, the occurrence of a leak in a pressure vessel can be detected without stopping the plant even during operation, and the leak position can be identified, resulting in energy savings. It is possible to eliminate negative effects on the equipment and peripheral equipment, and it also frees workers from working in adverse environments.

[Brief explanation of the drawing]

Fig. 1 is a block diagram showing an embodiment of the pressure vessel leak detection device of the present invention, Fig. 2 is an explanatory diagram showing the relationship between the acoustic sensor and the leak position, and Fig. 3 shows an example of the output of the acoustic sensors 2a and 2c. 4 is a graph illustrating a cross-correlation function, FIG. 5 is an explanatory diagram illustrating a leak position identification method, and FIGS. 6 and 7 are block diagrams illustrating other embodiments of the present invention, respectively. 8 and 9 are graphs illustrating the output of the acoustic sensor and the cross-correlation function in the embodiment of FIG. 7, and FIG. 10 is a perspective view showing another example of application of the present invention. 1...Condenser body outer wall 2a to 2e, 23a, 23b=--Acoustic sensors 3a to 3e...Preamplifiers 4a to 4e...Main amplifiers 5a, 5b ... Cross correlation analysis device 6 a s 6 b ... Acoustic signal arrival time difference signal 7.
......Leak position identification device 8...
・・Leak judgment bag 9・・・Calculation unit 3・・Comparator 4・・・Switcher 5・・・・・・・... Vibration device 6 ... Control device 7a to 17d ... Filter 8 ... Horn 0 ... Piping 1 ...・・・・・・Stop valve 2・・・・・・Blind flange

Claims (1)

[Claims] Three or more acoustic sensors are installed non-linearly on the outer wall of the pressure vessel to measure the sound propagating through the outer wall, and the signals from these acoustic sensors are led to a leak determination device and compared with the acoustic signal under normal conditions. The presence or absence of a leak is determined by this, and the outputs of the acoustic sensors are combined two by two and input into a cross-correlation analyzer to calculate the acoustic signal arrival time difference, and a signal indicating the acoustic signal arrival time difference is leaked. A pressure vessel leak detection device, characterized in that the pressure vessel leak detection device is configured to input information to a position identification device to identify a leak position.